The present invention relates to a grinding apparatus for grinding a groove in a cylindrical peripheral surface of a workpiece with a grinding wheel in which a convex grinding surface is formed on the outer peripheral surface.
Internal cylindrical grinding machines are known as grinding apparatuses for performing finish grinding on raceway grooves formed in inner peripheral surfaces of outer rings of ball bearings.
Conventional internal cylindrical grinding machines have used contact type rolling bearings as bearings for rotationally supporting a wheel spindle, on which a grinding wheel is mounted, on a casing of a spindle apparatus (see, e.g., JP-A-2001-159421 and JP-A-57-27660).
As described above, the conventional internal cylindrical grinding machine for performing finish grinding on a groove formed on the inner peripheral surface of the outer ring of the ball bearing uses the rolling bearing for rotationally supporting a wheel spindle. Thus, the conventional internal cylindrical grinding machine has the following problems that have occurred when grinding a raceway groove of the outer ring.
In the case of performing finish grinding on the raceway groove of the outer ring using the internal cylindrical grinding machine, a work (workpiece) in which a groove is formed on the inner peripheral surface in the preceding process, is rotated in a state in which the work is grasped by a gasping device, such as a chuck. In addition, a casing is positioned in an axial direction of the wheel spindle. Subsequently, the casing is radially moved so as to bring the grinding wheel into contact with the work and as to grind the groove.
At that time, in a case where there is no error in the axial position of the groove formed in the inner peripheral surface of the work in the preceding process, no problems are caused. However, in a case where an error in the axial position exists, and where the axial position of the groove is deviated from a correct axial position, a part of the grinding surface of the grinding wheel is extremely worn away. That is, what is called a grinding wheel wear occurs, so that the life of the grinding wheel is shortened.
For example, in a case where the position of a groove R of a work W is correct, as illustrated in FIG. 7A, the grinding surface S of a grinding wheel G is substantially simultaneously put into contact with the entire groove R when a casing is radially moved. Thus, the grinding surface S is not locally worn away. On the other hand, in a case where the position of the groove R is axially shifted to the left, as viewed in FIG. 7B, only the right-side edge of the groove R is put into contact with the grinding surface S of the grinding wheel and is ground when the casing is radially moved. Consequently, only a part of the grinding surface S of the grinding wheel, which is contacted with the right-side edge of the groove R, is locally worn away. Similarly, in a case where the position of the groove R is axially shifted to the right side, as viewed in FIG. 7C, only a part of the grinding surface S of the grinding wheel, which is contacted with the left-side edge of the groove R, is locally worn away.
Similar problems occur in the case of grinding a groove formed in a cylindrical peripheral surface (i.e., an inner peripheral surface or an outer peripheral surface) of a work, in addition to the case of performing finish grinding on the raceway groove of the inner peripheral surface of the outer ring.